The Mole Concept Introduction Number of Particles and Moles Topic 1.2

1. The Mole ConceptIntroductionNumber of Particles and MolesTopic 1.2

3. Dimensional Analysis • starting with one unit of measurement and ending up with a different one • “cancel out” what you don’t want • use conversion factors (fraction that equals one) • the numerator will contain the unit you want • the denominator will contain the unit you are trying to get rid of • try to predict a “ball park answer” if possible so you might recognize a wrong answer

5. sometimes they can be done in one step • example: 23,532 seconds = ? minutes 23,532 sec.X 1 min. 1 60 sec. 392.20 min.

6. sometimes they take multiple steps • example: 23,532 seconds = ? hours 23,532 sec.X 1 min. X 1 hour = 1 60 sec. 60 min. 6.5367 hours

7. but if you don’t know the conversion factor(s), the problem becomes impossible • example: 750 ml = ? floz 750 ml X 1 floz 1 29.6 ml 25.3 floz

8. How many minutes are in 2.5 hours? Initial unit 2.5 hr Conversion Final factor unit 2.5 hr x 60 min = 150 min 1 hr cancel Answer (2 SF) LecturePLUS Timberlake

9. How many seconds are in 1.4 days? What iswrong with the following setup? 1.4 day x 1 day x 60 min x 60 sec 24 hr 1 hr 1 min

10. How many seconds are in 1.4 days? 1.4 day x 1 day x 60 min x 60 sec 24hr 1 hr 1 min Units would be = day2(sec)/hr2 Not the final unit needed

11. Topic 1.2 really starts here

12. Measuring Matter • By counting • simply a number or moles • By determining the mass • grams • By determining the volume • liters

13. Not these! The Mole Not this!

14. the mole is a unit used in chemistry to represent a large number of particles such as… • atoms (Ne, Ar…) • molecules (H2O, CO2…) • ionic compounds (NaCl, MgCl2…) • ions (Mg2+,Cl1-…) • similar to a dozen, except instead of 12, it’s 602 billion trillion • 6.02 x 1023 or 602,214,199,000,000,000,000,000 • known as Avogadro’s number

15. 1 dozen cookies = 12 cookies • 1 mole of cookies = 6.02 X 1023 cookies • 1 dozen cars = 12 cars • 1 mole of cars = 6.02 X 1023 cars • 1 dozen Al atoms = 12 Al atoms • 1 mole of Al atoms = 6.02 X 1023 atoms Note that the NUMBER is always the same, but the MASS would be very different! Mole is abbreviated mol (gee, that’s a lot quicker to write, huh?)

16. 1 mole C • 6.02 x 1023 C atoms • 1 mole water • 6.02 x 1023H2O molecules • 1 mole NaCl • 6.02 x 1023NaCl ionic compounds (formula units) • 6.02 x 1023 Na+ ions • 6.02 x 1023Cl– ions

17. Note that a particle could be an atom OR a compound OR a molecule! • for counting in chemistry, the conversion factor will be: • 1 mole 6.02 x 1023 particles OR • 6.02 x 1023 particles 1 mole

18. Number of particles to moles • How many moles in 5.68 x 1025 fluorine molecules? 5.68 x 1025F2 molecules x_____1 mole____ 1 6.02 x 1023 molecules = 94.4 mol F2

19. How many moles of water in 7.77x1024 molecules of water? • 7.77 x 1024moleculesH2O x 1mole 6.02x1023 molecules • = 12.9 moles H2O

20. Number of moles to particles • How many atoms in 5.59 moles of He? 5.59 moles He x6.02 x 1023 atoms 1 1 mole = 3.36 x 1024 atoms • How many atoms in 2.98 moles of H20 molecules? 2.98 moles x6.02 x 1023 molecules H2O x 3 atoms 1 1 mole 1 molecule H2O = 5.38 x 1024 atoms